Change of employer while H1B extension is pending by current employer

[H1B for K]

Hi all,

I got a question but first lets go through my situation. Came to the US under J1. Got H1B with company in 2011. Company went down and I went to get an academia job bringing my H1b (industry H1B). My current H1b and I 94 expires 8/31/2015. Extension has been filed on April 15. Got a receipt but no news on the approval yet.
My GC via family petition has been filed early this year.

1: So I have been looking for a job, got interviews but the question is can I change employer before my current H1B extension is approved? Would that mean any issues to H1B extension approval started by current employer or with the new employer that would do the H1B change of employer process?

2: Would this (1) mean any problem for GC process.

3: Should I wait for the current H1B extension approval or just go ahead and change job with change of employer process?

4: How long does it take to have H1B extension approved in 2015?


Thanks! I appreciate your help!

K